A quantum dot infrared photodetector (QDIP) is a device that can detect infrared radiation. The detection of radiation is based on quantum mechanical principles that describe the absorption and radiation of light from atoms and molecules. A quantum dot (QD) is a defect purposely grown in a crystal structure (typically in some III-V semiconducting material such as InAs/GaAs structures). The defect is approximately the size of the wavelength of an electron in the crystal (≦100 nm).
The QD creates a 3-d localized attractive potential herein referred as a potential hole. Since the electrons are confined in 3-d to the QD whose size is of the order of the electron wavelength, electrons will have discrete energy levels, similar to discrete energy levels of an electron in an atom. The magnitude and spacing of these energy levels is a sensitive function of the dot and the magnitude of the attractive potential energy “potential hole.” Thus, by controlling the size and potential of the QD (through appropriate crystal growth techniques), one can create QDs sensitive to different wavelengths of light (colors). Photons incident on the crystal structure with the QDs will be absorbed if they have the energy (wavelength) corresponding to the separation of the ground and first excited energy state (it is possible to excite electrons into higher order states, but has a lower probability of occurrence). An electric field applied to the QDs sweeps the excited electrons off of the dot, and the change in current is measured thereby detecting the light.
What is currently needed are techniques for employing QDIP technology in focal plane array applications, where one or more colors can be detected. In addition, techniques for hybridizing QDIP arrays to supporting electronic circuitry (e.g., such as CMOS read-out circuitry) are needed.